United Scientific 55204 Polypropylene Vacuum Desiccator with Polycarbonate Cover - 6 Inch (152.4mm) Diameter - Ideal for Laboratory Moisture Control & Chemical Storage

This is a nice compact unit. I tested it yesterday with one of the hand operated vacuum pumps. The pump goes up to 725ml IIRC. I pumped it down to around 400 and left the vacuum chamber connected. 24 hours late, the gauge on the pump had not moved. So there appears to be no leakage of any kind, to any degree.Some reviews have complained about the valve. This comes separate from the unit and you have to install it. However this is very simple to do. It requires some gentle force twisting the valve back and forth as you try to get it to seat, but it WILL go all the way on with a little persistence. Once mated to the dome, it's very secure.The only issue I have with the device and it's minor, is that to get the vacuum started and the seal fully engaged, it helps if you press down on the dome until you register some amount of vacuum on you pump. But once seated, you only need to worry about pumping and watching your gauge.